Sulfate Peak Research Articles

New estimates of sulfate diffusion rates in the EPICA Dome C ice core

Abstract. To extract climatically relevant chemical signals from the deepest, oldest Antarctic ice, we must first investigate the degree to which chemical ions diffuse within solid ice. Volcanic sulfate peaks are an ideal target for such an investigation because they are high-amplitude, short-duration (∼3 years) events with a quasi-uniform structure. Here we present an analysis of the EPICA Dome C sulfate record over the last 450 kyr. We identify volcanic peaks and isolate them from the non-sea-salt sulfate background to reveal the effects of diffusion: amplitude damping and broadening of peaks in the time domain with increasing depth and age. Sulfate peak shape is also altered by the thinning of ice layers with depth that results from ice flow. Both processes must be simulated to derive effective diffusion rates. This is achieved by running a forward model to diffuse idealised sulfate peaks at different rates while also accounting for ice thinning. Our simulations suggest a median effective diffusion rate of sulfate ions of 2.4±1.7×10-7 m2 yr−1 in Holocene ice, slightly faster than suggested by previous work. The effective diffusion rate observed in deeper ice is significantly lower, and Holocene ice shows the highest rate of the last 450 kyr. Beyond the Holocene, there is no systematic difference between the effective diffusion rates of glacial and interglacial periods despite variations in soluble ion concentrations, dust loading, and ice grain radii. Effective diffusion rates for 40 to 200 ka are relatively constant and of the order 1×10-8 m2 yr−1. Our results suggest that the diffusion of sulfate ions within volcanic peaks is relatively fast initially, perhaps through an interconnected vein network, but slows significantly after 40 kyr. In the absence of clear evidence for a controlling influence of temperature on sulfate diffusivity with depth and age, we hypothesise that the rapid decrease in effective diffusion rate from the time of deposition to ice of 50 ka age may be due to a switch in the mechanism of diffusion resulting from the changing location of sulfate ions within the ice microstructure and/or interconnectedness of veins and grain boundaries.

Characterizing Hydrated Sulfates and Altered Phases in Jezero Crater Fan and Floor Geologic Units With SHERLOC on Mars 2020

AbstractThe Mars 2020 Perseverance rover has explored fluvio‐lacustrine sedimentary rocks within Jezero crater. Prior work showed that igneous crater floor Séítah and Máaz formations have mafic mineralogy with alteration phases that indicate multiple episodes of aqueous alteration. In this work, we extend the analyses of hydration to targets in the Jezero western fan delta, using data from the SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) Raman spectrometer. Spectral features, for example, sulfate and hydration peak positions and shapes, vary within, and across the crater floor and western fan. The proportion of targets with hydration associated with sulfates was approximately equal in the crater floor and the western fan. All hydrated targets in the crater floor and upper fan showed bimodal hydration peaks at ∼3,200 and ∼3,400 cm−1. The sulfate symmetric stretch at ∼1,000 cm−1 coupled with a hydration peak at ∼3,400 cm−1 indicate that MgSO4·nH2O (2 < n ≤ 5) is a likely hydration carrier phase in all units, perhaps paired with low‐hydration (n ≤ 1) amorphous Mg‐sulfates, indicated by the ∼3,200 cm−1 peak. Low‐hydration MgSO4·nH2O (n = 1–2) are more prevalent in the fan, and hydrated targets in the fan front only had one peak at ∼3,400 cm−1. While anhydrite co‐occurs with hydrated Mg‐sulfates in the crater floor and fan front, hydrated Ca‐sulfates are observed instead at the top of the upper fan. Collectively, the data imply aqueous deposition of sediments with formation of salts from high ionic strength fluids and subsequent aridity to preserve the observed hydration states.

Diagnosis of durability-related problems in concrete structures through comprehensive analysis and non-destructive testing: a case study

ABSTRACT The present study investigated concrete durability problems at the National University of Sciences and Technology,Pakistan, through comprehensive analysis and non-destructive testing. During the visual inspection of concrete structures, different deterioration mechanisms such as alkali-silica aggregate reaction (ASR), carbonation, abrasion and drying shrinkage were found. After visual inspection, the data on ingredients used in the construction of various structures were collected, revealingthat different brands of cement used in construction contained high alkali-equivalent content. Fine aggregates were used from two different quarries during construction. The available literature and X-ray Diffraction (XRD) results showed that both the quarries’ aggregates have the potential for alkali-silica reactivity. Furthermore, the XRD results of gel-type material collected from mapped cracking indicated the presence of delhayelite, similar to alkali-silica gel, suggesting ASR. The XRD curves of the whitest powder collected from various sites showed the presence of sodium sulfate and calcium carbonate peaks, indicating salt hydration attacks. The carbonation rate in concrete ranges from 4.33 to 5.77 mm/year. The results of the rebound hammer and pulse velocity test indicated that concrete used in parking has low strength which is the main cause of abrasion. Based on these findings a few recommendations have been presented to avoid durability-related problems in future structures.

RP-HPLC Method Development and Validation for Simultaneous Estimation of Escitalopram Oxalate and Atazanavir Sulphate in Bulk and Dosage Form

Background: This study was designed for the estimation of escitalopram oxalte and atazanavir sulphate in the experimental tablet formulation. The separation was performed at 210 nm by using Inertsil ODS 3V (250 * 4.6 mm, 5.0 m) column and acetonitrile/phosphate buffer (pH =3.55) as the eluent under isocratic elution conditions at a flow rate of 1.0 mL/min. Results: Escitalopram oxalate and atazanavir sulphate peaks were eluted at 2.636 and 3.319 minutes and no interference was observed in the diluent blank at the respective retention times, indicating that the developed method was specific and selective. A linear relationship was found for escitalopram oxalte (2.5 - 15 µg mL-1) and atazanavir sulphate (30 - 150.0 µg mL-1), with coefficient of regression greater than 0.999. Based on the RSD values (< 2.0%) and recovery results (> 98%), the developed method is accurate. At room temperature and in the refrigerated conditions, standard and sample solutions of escitalopram oxalate and atazanavir sulphate have been found to be stable for 48 hours. Conclusion: The established method is linear, precise, accurate, specific, and robust in the studied concentration range. Accordingly, the proposed method can be applied to the analysis of experimental tablet formulations as well as bulk drug samples.

Determination of trace perchlorate in river water by ion chromatography with online matrix removal and sample concentration.

This paper proposes a simple ion chromatographic approach to determine trace amounts of perchlorate in river water samples. Determination of the trace perchlorate by ion chromatography typically faces two challenges: interference by matrix ions such as chloride, nitrate, and sulfate in the samples and insufficient detection sensitivity. In the present study, online pretreatment of the samples with an OnGuard II Ba/Ag/H disposable sample pretreatment cartridge prevented the sulfate peak tailing from overlapping with the perchlorate peak on the chromatogram. In addition, the matrix removal enabled as large as 10mL of sample to be loaded into a high exchange capacity anion concentrator, significantly improving perchlorate's detection sensitivity. The proposed approach achieved a detection limit (S/N = 3) of 0.046µg L-1 without using a costly mass spectrometer and successfully determined sub µgL-1 levels of perchlorate in river water.

A sulfur and halogen budget for the large magmatic system beneath Taupō volcano

The transport and degassing pathways of volatiles through large silicic magmatic systems are central to understanding geothermal fluid compositions, ore deposit genesis, and volcanic eruption dynamics and impacts. Here, we document sulfur (S), chlorine (Cl), and fluorine (F) concentrations in a range of host materials in eruptive deposits from Taupō volcano (New Zealand). Materials analysed are groundmass glass, silicic melt inclusions, and microphenocrystic apatite that equilibrated in shallow melt-dominant magma bodies; silicic melt and apatite inclusions within crystal cores inferred to be sourced from deeper crystal mush; and olivine-hosted basaltic melt inclusions from mafic enclaves that represent the most primitive feedstock magmas. Sulfur and halogen concentrations each follow distinct concentration pathways during magma differentiation in response to changing pressures, temperatures, oxygen fugacities, crystallising mineral phases, the effects of volatile saturation, and the presence of an aqueous fluid phase. Sulfur contents in the basaltic melt inclusions (~ 2000 ppm) are typical for arc-type magmas, but drop to near detection limits by dacitic compositions, reflecting pyrrhotite crystallisation at ~ 60 wt. % SiO2 during the onset of magnetite crystallisation. In contrast, Cl increases from ~ 500 ppm in basalts to ~ 2500 ppm in dacitic compositions, due to incompatibility in the crystallising phases. Fluorine contents are similar between mafic and silicic compositions (< 1200 ppm) and are primarily controlled by the onset of apatite and/or amphibole crystallisation and then destabilisation. Sulfur and Cl partition strongly into an aqueous fluid and/or vapour phase in the shallow silicic system. Sulfur contents in the rhyolite melts are low, yet the Oruanui supereruption is associated with a major sulfate peak in ice core records in Antarctica and Greenland, implying that excess S was derived from a pre-eruptive gas phase, mafic magma recharge, and/or disintegration of a hydrothermal system. We estimate that the 25.5 ka Oruanui eruption ejected > 130 Tg of S (390 Tg sulfate) and up to ~ 1800 Tg of Cl, with potentially global impacts on climate and stratospheric ozone.

THE ANTIOXIDANT ACTIVITIES OF ACID HYDROLYSIS OF κ-Carrageenan

Carrageenans are naturally sulphated polysaccharides produced by primary metabolism in red seaweed (Rhodophyceae). Carrageenans are thought to be a good source of antioxidants. The antioxidant activity of commercial κ-Carrageenan and degraded κ-Carrageenan will be determined in this investigation. Hydrochloric acid was used to hydrolyzed κ-Carrageenan. A 3500 Da molecular weight dialysis tube was also used to separate the filtrate (MW 3500 Da). UV-Vis, FTIR, and GC-MS spectroscopies were used to analyze the chemical and spectral properties of commercial Carrageenan and its degradation products. The antioxidant activity of the compounds was determined using 2,2-diphenyl-2-picryl-hydrazyl (DPPH) and compared to vitamin C as a standard using UV at a wavelength of 517 nm in the concentration range of 200 - 800 ppm. The chemical structure of the degraded κ-Carrageenan was disclosed by FTIR analysis, which demonstrated a decrease in the intensity of the sulfate peak and the production of new carbonyl groups. Hexadecanoic acid ethyl ester, 1,2-benzenedicarboxylic acid, 9,19-Cyclo-9β-lanostan-3β-ol, 24-methylene-, and (E,E,E,E,E,E)-(1)-2,6,10,15,19,23-hexamethyltetracosa-1,6,10,14,18,22-hexaen-3-ol were found in the GC-MS. Analysis antioxidant activities of commercial κ-Carrageenan, degraded κ-Carrageenan with a molecular weight over 3500 Da, and κ-Carrageenan with a molecular weight below 3500 Da, respectively, have range percent inhibition from 7.83 - 13.58%, 32.64 - 42.28%, and 26.63% - 34.99%. Vitamin C, on the other hand, has a percent inhibition of 97.65% - 99.48%

DEVELOPMENT OF THE METHOD FOR QUANTITATIVE DETERMINATION OF NEOMYCIN SULPHATE IN VETERINARY PREPARATIONS WITH PRECOLUMN DERIVATIZATION AND FLUORESCENT DETECTION

The aim of work was to develop a method for the identification and quantification of neomycin sulfate in intracisternal veterinary preparations. The method was developed and validated by: selectivity, linearity and suitability parameters of the chromatographic system. A four-component intracisternal drug with a 25 mg/g neomycin content was used as an object sample for method development. The standard sample and the test sample were dissolved in purified water to a concentration of 100 μg/ml, followed by derivatization with 9-fluorenylmethoxycarbonyl chloride at room temperature. The total uncertainty of the analysis was 1.62 %, which is within the limits recommended in SFU 2.0. The samples were separated on a Dionex Ultimate 3000 chromatograph equipped with an Acclaim C18 150 × 4.6.5 μm chromatographic column. The mobile phase was a mixture of acetonitrile and water in a volume ratio of 95:5. Neomycin sulfate was detected fluorescently at wavelengths λex - 254 nm, λem - 303 nm.&#x0D; Under the above conditions, it was possible to completely separate the two isoforms of neomycin (retention time of chromatographic peaks - 6.57 min and 6.98 min), 9-fluorenylmethoxycarbonyl chloride and other components of the study drug (retention time of the corresponding chromatographic peaks - 2-5 min). In this case, the parameters of the suitability of the chromatographic system did not exceed the limits specified in the recommendations of the USA Food and Drug Association. For peaks of neomycin sulfate, the efficiency of the chromatographic system was 7700–7950 theoretical plates. The relative standard deviation (RSD) for the peak areas of the active substance was ± 0.33%, and the coefficient of separation of the peaks (RS) of neomycin sulfate from the peaks of the derivatization reagent and other components of the drug was 11.9. The coefficient of peak symmetry was 1.18. The calibration curves were linear in the recommended SFU 2.0 range (80–120% of the nominal concentration of the corresponding active substance). The coefficient of linearity (R2) for the sum of neomycin sulfate peak areas was – 0.9991.

Effect of Sulphur-Containing Tailings Content and Curing Temperature on the Properties of M32.5 Cement Mortar.

The effect of the dosage of sulphur-containing tailings (STs) and curing temperature on the properties of M32.5 cement mortar was studied in this work. An experimental study was conducted to evaluate the effects of STs with different substitution ratios (0, 10%, 20%, 30%, 40%) on the compressive strength experiment, fluidity, expansion ratio, and pore structure of M32.5 cement mortar. The results showed that the addition of STs reduced the fluidity of mortar, and the fluidity decreased with the increase of the STs dosage. The compressive strength of mortars increased at a lower substitution rate (0~20%) but decreased at a higher substitution rate (>20%). Ettringite peaks and new sulfate peaks were found by X-ray diffraction (XRD) analysis. Scanning electron microscope (SEM) observation of the microstructure showed that a large number of hydrated products, such as ettringite, formed and filled in the interstitial space, which was conducive to the development of strength. The optimal STs replacement ratio of river sand was 10%. Then, the performance of mortar at curing temperatures of 23 ± 1, 40, 60, and 80 °C was further investigated under the optimal STs replacement ratio. Under high-temperature curing conditions, the early strength of M32.5 cement mortar with STs increased greatly, but the late strength decreased gradually with the increase in curing temperature. The early strength development of the mortar mainly depended on the high speed of hydration reaction, and the late strength variation was mainly affected by hydration products and the pore size distribution. After comprehensive consideration, the optimal curing temperature of M32.5 cement mortar with STs was 40 °C.

Polyaniline nanofibers, a nanostructured conducting polymer for the remediation of Methyl orange dye from aqueous solutions in fixed-bed column studies

Polyaniline nanofibers (PANI NFs) were synthesized and employed as potential adsorbents in a continuous flow fixed-bed column adsorption study for an organic dye, Methyl Orange (MO) removal from water. These nanostructured adsorbents were characterized using ATR-FTIR, FE-SEM, HR-TEM, TGA, BET, XRD, XPS, and the Zeta-sizer. Morphological representations from SEM and TEM analyses showed that the fibers were nanosized with diameters lower than 80 nm and an interconnected network possessing a smooth surface. The SBET of the PANI NFs was found to be 35.80 m2/g. The impact of column design parameters for instance; influent concentration, flow rate, and bed mass was investigated using pH 4 influent MO solutions optimized through batch studies. The best influent concentration, bed length, and flow rate for this study were determined as 25 mg/L, 9 cm (6 g), and 3 mL/min, respectively. The column information was fitted in Thomas, Yoon-Nelson, and Bohart-Adams models. It appeared that the Thomas and Yoon-Nelson models described the data satisfactorily. The PANI NFs were able to treat 29.16 L of 25 mg/L MO solution at 9 cm bed length. A sulfate peak in a de-convoluted sulfur spectrum using XPS verified the successful adsorption of Methyl Orange.

Cryptotephra from the Icelandic Veiðivötn 1477 CE eruption in a Greenland ice core: confirming the dating of volcanic events in the 1450s CE and assessing the eruption's climatic impact

Abstract. Volcanic eruptions are a key source of climatic variability, and reconstructing their past impact can improve our understanding of the operation of the climate system and increase the accuracy of future climate projections. Two annually resolved and independently dated palaeoarchives – tree rings and polar ice cores – can be used in tandem to assess the timing, strength and climatic impact of volcanic eruptions over the past ∼ 2500 years. The quantification of post-volcanic climate responses, however, has at times been hampered by differences between simulated and observed temperature responses that raised questions regarding the robustness of the chronologies of both archives. While many chronological mismatches have been resolved, the precise timing and climatic impact of two major sulfate-emitting volcanic eruptions during the 1450s CE, including the largest atmospheric sulfate-loading event in the last 700 years, have not been constrained. Here we explore this issue through a combination of tephrochronological evidence and high-resolution ice-core chemistry measurements from a Greenland ice core, the TUNU2013 record. We identify tephra from the historically dated 1477 CE eruption of the Icelandic Veiðivötn–Bárðarbunga volcanic system in direct association with a notable sulfate peak in TUNU2013 attributed to this event, confirming that this peak can be used as a reliable and precise time marker. Using seasonal cycles in several chemical elements and 1477 CE as a fixed chronological point shows that ages of 1453 CE and 1458 CE can be attributed, with high precision, to the start of two other notable sulfate peaks. This confirms the accuracy of a recent Greenland ice-core chronology over the middle to late 15th century and corroborates the findings of recent volcanic reconstructions from Greenland and Antarctica. Overall, this implies that large-scale Northern Hemisphere climatic cooling affecting tree-ring growth in 1453 CE was caused by a Northern Hemisphere volcanic eruption in 1452 or early 1453 CE, and then a Southern Hemisphere eruption, previously assumed to have triggered the cooling, occurred later in 1457 or 1458 CE. The direct attribution of the 1477 CE sulfate peak to the eruption of Veiðivötn, one of the most explosive from Iceland in the last 1200 years, also provides the opportunity to assess the eruption's climatic impact. A tree-ring-based reconstruction of Northern Hemisphere summer temperatures shows a cooling in the aftermath of the eruption of −0.35 ∘C relative to a 1961–1990 CE reference period and −0.1 ∘C relative to the 30-year period around the event, as well as a relatively weak and spatially incoherent climatic response in comparison to the less explosive but longer-lasting Icelandic Eldgjá 939 CE and Laki 1783 CE eruptions. In addition, the Veiðivötn 1477 CE eruption occurred around the inception of the Little Ice Age and could be used as a chronostratigraphic marker to constrain the phasing and spatial variability of climate changes over this transition if it can be traced in more regional palaeoclimatic archives.

The reductions of oxalate and its precursors in cloud droplets relative to wet particles

Abstract The formation mechanism of oxalate in the aqueous phase remains uncertain. Approximately 600 000 oxalate-containing particles and 450 000 its precursors-containing particles (e.g., acetate, glyoxylate, pyruvate and malonate) were obtained using a single particle aerosol mass spectrometer at a mountain site in southern China from 9 May to 4 June, 2018. The number fraction of oxalate or its precursors was compared within three representative aerosols with different liquid water contents including cloud droplet residues (RES), cloud interstitial particles (INTER) and cloud-free ambient particles (AMB). Lower number fraction of oxalate was found in the RES relative to INTER and AMB, mostly attributed to the decrease in precursors. This was conflicted with the enhancement of in-cloud oxalate formation previously reported. Further analysis indicated that the aerosol acidity had a major influence on the formation of precursors and their conversion to oxalate. With the increase of relative aerosol acidity (defined as the sum of sulfate and nitrate peak areas divided by ammonium peak area), the formation of precursors was increased while the conversion of precursors to oxalate was suppressed. Meanwhile, this influence was more pronounced in the INTER and AMB relative to RES. This work highlighted the roles of aerosol acidity and liquid water content in the aqueous phase formations of oxalate and its precursors.

TRACE LEVEL DETERMINATION OF SODIUM CHLORIDE AND SODIUM SULFATE CONTENT IN SODIUM LAURETH SULFATE RAW MATERIAL USING COUNTER CATION-EXCHANGE HPLC WITH INDIRECT ULTRAVIOLET DETECTION

Objective: A novel study on a new liquid chromatographic approach has been developed and validated for simultaneous determination of trace level determination of sodium chloride and sodium sulfate measures its impurities using counter cation-exchange high-performance liquid chromatography with indirect ultraviolet (UV) detection.&#x0D; Methods: Chromatographic separation is developed and validated on a Hamilton PRP-X100 column with a mobile phase contained a mixture of the para-hydroxybenzoic acid buffer with a pH of 9.0 and methanol. Chromatography is developed at a flow rate of 2.0 mL/min with an indirect UV determination at 310 nm at a sensitivity level of 0.5%. The optimized method was validated as per the ICH Q2 guidelines.&#x0D; Results: The retention times of chloride and sulfate were about 2.8 and 7.6 min, respectively. The resolution between chloride and sulfate peaks is &gt;4. Regression analysis confers a correlation coefficient for the stated compounds that are found to be &gt;0.999.&#x0D; Conclusion: A novel analytical method was validated as per the ICH method validation guidelines and found to be selective. Hence, the validated analytical method was precise, specific, and accurate, and it is more economic and simple for the determination of inorganic impurities.

Volcanic glass properties from 1459 C.E. volcanic event in South Pole ice core dismiss Kuwae caldera as a potential source

A large volcanic sulfate increase observed in ice core records around 1450 C.E. has been attributed in previous studies to a volcanic eruption from the submarine Kuwae caldera in Vanuatu. Both EPMA–WDS (electron microprobe analysis using a wavelength dispersive spectrometer) and SEM–EDS (scanning electron microscopy analysis using an energy dispersive spectrometer) analyses of five microscopic volcanic ash (cryptotephra) particles extracted from the ice interval associated with a rise in sulfate ca. 1458 C.E. in the South Pole ice core (SPICEcore) indicate that the tephra deposits are chemically distinct from those erupted from the Kuwae caldera. Recognizing that the sulfate peak is not associated with the Kuwae volcano, and likely not a large stratospheric tropical eruption, requires revision of the stratospheric sulfate injection mass that is used for parameterization of paleoclimate models. Future work is needed to confirm that a volcanic eruption from Mt. Reclus is one of the possible sources of the 1458 C.E. sulfate anomaly in Antarctic ice cores.

Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores

The record of volcanic forcing of climate over the past 2500 years is based primarily on sulfate concentrations in ice cores. Of particular interest are large volcanic eruptions with plumes that reached high altitudes in the stratosphere, as these afford sulfate aerosols the longest residence time in the atmosphere, and thus have the greatest impact on radiative forcing. Sulfur isotopes measured in ice cores can be used to identify these large eruptions because stratospheric sulfur is exposed to UV radiation, which imparts a time-evolving mass independent fractionation (MIF) that is preserved in the ice. However, sample size requirements of traditional measurement techniques mean that the MIF signal may be obscured, leading to an inconclusive result. Here we present a new method of measuring sulfur isotopes in ice cores by multi-collector inductively coupled plasma mass spectrometry, which reduces sample size requirements by three orders of magnitude. Our method allows us to measure samples containing as little as 10 nmol of sulfur, with a precision of 0.11‰ for δ34S and 0.10‰ for Δ33S, enabling a high-temporal resolution over ice core sulfate peaks. We tested this method on known tropical (Tambora 1815 and Samalas 1257) and extra-tropical (Katmai/Novarupta 1912) stratospheric eruptions from the Tunu2013 ice core in Greenland and the B40 ice core from Antarctica. These high-resolution sulfur isotope records suggest a distinct difference between the signatures of tropical versus extra-tropical eruptions. Furthermore, isotope mass balance on sulfate from extra-tropical eruptions provides a means to estimate the fraction of sulfate deposited that was derived from the stratosphere. This technique applied to unidentified eruptions in ice cores may thus improve the record of explosive volcanism and its forcing of climate.

Sulfur K-edge XAS study of sulfur transformation behavior during pyrolysis and co-pyrolysis of biomass and coals under different atmospheres

Three low rank coals and one biomass, YiMa (YM) and Chifeng (CF) with comparatively high FeS2, and Ximeng (XM) coals with high organic sulfur contents, and sawdust (SD), were selected to investigate sulfur transformation behavior during pyrolysis and co-pyrolysis under Ar and CO2 atmospheres. The sulfur transformation of those samples was investigated by X-ray absorption spectroscopy (XAS) combined with X-ray fluorescence (XRF). For SD, the coals and their mixtures, the subordinate peak of CaS is formed during pyrolysis under Ar atmosphere, but not under CO2 atmosphere. For XM and CF coals, sulfate peak of their chars and the chars of their mixture becomes more intense after pyrolysis under Ar atmosphere, while remain low under CO2 atmosphere. This indicates that CO2 atmosphere can impede the formation of CaS and sulfate. In addition, CO2 atmosphere and SD can promote the decomposition of FeS in CF coal before 900 °C, while SD has no significant effect on FeS in YM coal at the ratio of 3:1 (YM:SD). However, SD can also help the decomposition of FeS in YM coal at the ratio of 1:1. This suggests that SD is not enough for FeS to decompose at the ratio of 3:1. Thiophene peaks of all samples are more intense under CO2 atmosphere than under Ar atmosphere, meaning that more stable organic sulfur is formed and retained in the char after pyrolysis and co-pyrolysis under CO2 atmosphere.

Characteristics and mixing state of amine-containing particles at a rural site in the Pearl River Delta, China

Abstract. Particulate amines play an important role for the particle acidity and hygroscopicity and also contribute to secondary organic aerosol mass. We investigated the sources and mixing states of particulate amines using a single-particle aerosol mass spectrometer (SPAMS) during summer and winter 2014 at a rural site in the Pearl River Delta, China. Amine-containing particles accounted for 11.1 and 9.4 % of the total detected individual particles in summer and winter, respectively. Although the increase in amine-containing particle counts mostly occurred at night, no obvious correlations between amine-containing particles and ambient relative humidity (RH) were found during the sampling period. Among the three markers we considered, the most abundant amine marker was 74(C2H5)2NH2+, which was detected in 90 and 86 % of amine-containing particles in summer and winter, followed by amine marker ions of 59(CH3)3N+, and 86(C2H5)2NCH2+ which were detected in less than 10 % of amine-containing particles during sampling period. The amine-containing particles were characterized by high fractions of carbonaceous marker ions, carbon–nitrogen fragments, sulfate, and nitrate in both summer and winter. More than 90 % of amine-containing particles were found to be internally mixed with sulfate throughout the sampling period, while the percentage of amine particles containing nitrate increased from 43 % in summer to 69 % in winter. Robust correlations between the peak intensities of amines, sulfate, and nitrate were observed, suggesting the possible formation of aminium sulfate and nitrate salts. Interestingly, only 8 % of amine particles contained ammonium in summer, while the percentage increased dramatically to 54 % in winter, indicating a relatively ammonium-poor state in summer and an ammonium-rich state in winter. The total ammonium-containing particles were investigated and showed a much lower abundance in ambient particles in summer (3.6 %) than that in winter (32.6 %), which suggests the ammonium-poor state of amine-containing particles in summer may be related to the lower abundance of ammonia/ammonium in gas and particle phases. In addition, higher abundance of amines in ammonium-containing particles than that of ammonium in amine-containing particles suggests a possible contribution of ammonium–amine exchange reactions to the low abundance of ammonium in amine-containing particles at high ambient RH (72 ± 13 %) in summer. The particle acidity of amine-containing particles is estimated via the relative acidity ratio (Ra), which is defined as the ratio of the sum of the sulfate and nitrate peak areas divided by the ammonium peak area. The Ra was 326 ± 326 in summer and 31 ± 13 in winter, indicating that the amine-containing particles were more acidic in summer than in winter. However, after including amines along with the ammonium in the acidity calculation, the new Ra′ values showed no seasonal change in summer (11 ± 4) and winter (10 ± 2), which suggests that amines could be a buffer for the particle acidity of ammonium-poor particles.

XAS combined with TG–DTG study on synergic effect on sulfur transformation during co-pyrolysis of sawdust and lignite

The synergic effect of sawdust (SD) and a lignite can be observed by analyzing their co-pyrolysis behavior. The co-pyrolysis behavior of SD and lignite mixtures was investigated by thermo-gravimetric analysis, and their sulfur transformation was measured by X-ray absorption spectroscopy (XAS). The pyrolysis process can be divided into three stages for SD and lignite, while four their mixtures. The experimental mass loss of SD and lignite mixture during co-pyrolysis is higher than its theoretically calculated mass loss, especially at the mixing ratio of 1:1. This indicates that synergy occurs during SD and lignite co-pyrolysis process. XAS spectra of sulfur show that SD can promote FeS to decompose before 900 °C during co-pyrolysis, as the peak of FeS decreases in the mixture’s char. However, the experimental sulfur removal of mixtures is lower than the theoretically calculated one. This indicates that synergic effect has no effect on sulfur removal, which is very corresponding to more thiophenes gathering in the mixture’s char, because the peak of thiophenes is very steep for the mixture after pyrolysis. And other sulfurs transformation in the mixture is very similar to that of CF coal. For CF coal and its mixture, sulfate peak increases obviously after pyrolysis, which is mostly caused by absorbing SO2 of alkaline minerals during pyrolysis. This also suggests SD cannot prevent sulfate from forming during co-pyrolysis. Therefore, SD can be added to promote high-pyrite coal to increase sulfur removal, since the decomposition of FeS needs higher temperatures.

Rapid transport of ash and sulfate from the 2011 Puyehue‐Cordón Caulle (Chile) eruption to West Antarctica

AbstractThe Volcanic Explosivity Index 5 eruption of the Puyehue‐Cordón Caulle volcanic complex (PCC) in central Chile, which began 4 June 2011, provides a rare opportunity to assess the rapid transport and deposition of sulfate and ash from a midlatitude volcano to the Antarctic ice sheet. We present sulfate, microparticle concentrations of fine‐grained (~5 μm diameter) tephra, and major oxide geochemistry, which document the depositional sequence of volcanic products from the PCC eruption in West Antarctic snow and shallow firn. From the depositional phasing and duration of ash and sulfate peaks, we infer that transport occurred primarily through the troposphere but that ash and sulfate transport were decoupled. We use Hybrid Single‐Particle Lagrangian Integrated Trajectory back trajectory modeling to assess atmospheric circulation conditions in the weeks following the eruption and find that conditions favored southward air parcel transport during 6–14 June and 4–18 July 2011. We suggest that two discrete pulses of cryptotephra deposition relate to these intervals, and as such, constrain the sulfate transport and deposition lifespan to the ~2–3 weeks following the eruption. Finally, we compare PCC depositional patterns to those of prominent low‐ and high‐latitude eruptions in order to improve multiparameter‐based efforts to identify “unknown source” eruptions in the ice core record. Our observations suggest that midlatitude eruptions such as PCC can be distinguished from explosive tropical eruptions by differences in ash/sulfate phasing and in the duration of sulfate deposition, and from high‐latitude eruptions by differences in particle size distribution and in cryptotephra geochemical composition.

Antenatal risk factors associated with need of postpartum antihypertensives in women with preeclampsia in South India: Case control study.

To investigate the antepartum risk factors associated with the need for antihypertensive medication in the postpartum period in women with pre-eclampsia. Matched retrospective case control study was done in a tertiary center in south India between January 2016 and June 2016. We compared 100 preeclamptic women requiring antihypertensive medication in the postpartum period at discharge with 100 preeclamptic women who were not on antihypertensive medication at discharge, matched for age and parity at a ratio 1:1. Demographic data, maternal medical conditions, and delivery data were abstracted from maternal charts. Risk factors were evaluated using conditional logistic regression. Gestational age at delivery was comparable in both groups (34.3vs. 35.6weeks, p=0.220). Cesarean section rates were higher in the cases compared to controls (53% vs. 32%, p=0.004). After adjusting for age and parity women who had eclampsia, required prophylactic magnesium sulphate therapy and high peak antenatal systolic blood pressure were associated with postpartum antihypertensives. Using multivariate conditional logistic regression, mean systolic blood pressure (OR=1.03, 95% CI 1.00-1.07), development of eclampsia (OR=6.43, 95% CI 1.03-39.91) and need of prophylactic magnesium sulphate (OR=5.02, 95% CI 2.02-12.47) were found to be associated with the need of postpartum antihypertensives. In women with preeclampsia, development of eclampsia, use of prophylactic magnesium sulphate and high peak antenatal systolic blood pressure are more likely to require antihypertensives in postpartum period.